Light Mixer Generates 11 Colors Simultaneously

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An optical frequency mixer has been developed that uses a novel nanostructured metamaterial to concurrently generate 11 different colors of light. The metamaterial is made from an array of gallium arsenide (GaAs) nanocylinders. Each nanocylinder is only about 500 nm tall and about 400 nm in diameter. The nanostructures are laid out in a square pattern about 840 nm from each other. The tiny, repeating structures can interact with electromagnetic waves in ways that conventional materials cannot.

Current methods for mixing light use phase matching, a technique that uses crystals to align the lightwaves perfectly. Because a single crystal can efficiently match the phases of one color of incoming light only, it can produce just one different color of light.

Light mixer generates 11 colors simultaneously, Sandia National Laboratories

Sandia National Laboratories postdoctoral appointee Polina Vabishchevich (left) and senior scientist Igal Brener made a metamaterial that mixes two lasers to produce 11 colors ranging from the near infrared to ultraviolet. Courtesy of Randy Montoya/Sandia National Laboratories.

In a different approach, the team from Sandia National Laboratories used two NIR lasers with wavelengths tuned to the metamaterial’s resonant frequencies. Different mixing products were used to generate 11 different colors from the two laser pulses, without the need for phase matching.

The novel metamixer exploits the combined attributes of resonantly enhanced electromagnetic fields at the metasurface resonant frequencies; the even-order and odd-order optical nonlinearities of GaAs; and the relaxed phase-matching conditions.

Light mixer generates 11 colors simultaneously, Sandia National Laboratories

Sandia National Laboratories’ new light mixing metamaterial, made up of an array of nanocylinders, produces 11 colors. The infrared light is actually 10 times stronger than the red light. Courtesy of Michael Vittitow.

The even- and odd-order nonlinearities of the GaAs-based dielectric metasurface enabled a variety of simultaneous nonlinear optical processes across a broad spectral range. Specifically, seven different nonlinear processes (second-harmonic, third-harmonic, and fourth-harmonic generation; sum-frequency generation; two-photon absorption-induced photoluminescence; four-wave mixing; and six-wave mixing) were shown to simultaneously give rise to 11 new frequencies spanning the UV to NIR spectral range.

The research team believes that the ultracompact optical mixer could enable a number of applications in biology, chemistry, sensing, communications, and quantum optics that require light at specific wavelengths. The team further believes that the novel metasurface could be optimized for other nonlinear mixing processes such as difference frequency generation. This would enable the production of femtosecond pulses covering the mid-IR spectral range.

Though the conversion efficiency for the optical metamixer is very low, researcher Igal Brener believes the efficiency can be greatly improved with further work, perhaps by stacking multiple layers of metamaterial.

The research was published in Nature Communications (doi:10.1038/s41467-018-04944-9).

Published: July 2018
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
nonlinear optics
Nonlinear optics is a branch of optics that studies the optical phenomena that occur when intense light interacts with a material and induces nonlinear responses. In contrast to linear optics, where the response of a material is directly proportional to the intensity of the incident light, nonlinear optics involves optical effects that are not linearly dependent on the input light intensity. These nonlinear effects become significant at high light intensities, such as those produced by...
Nanophotonics is a branch of science and technology that explores the behavior of light on the nanometer scale, typically at dimensions smaller than the wavelength of light. It involves the study and manipulation of light using nanoscale structures and materials, often at dimensions comparable to or smaller than the wavelength of the light being manipulated. Aspects and applications of nanophotonics include: Nanoscale optical components: Nanophotonics involves the design and fabrication of...
Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free electrons in a metal or semiconductor at the nanoscale. Specifically, plasmonics deals with the collective oscillations of these free electrons, known as surface plasmons, which can confine and manipulate light on the nanometer scale. Surface plasmons are formed when incident photons couple with the conduction electrons at the interface between a metal or semiconductor...
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